Duplicating



Patented Jan. 25, 1927.

UNITED STATES J DAVD) GESTETNER, F TOTTENHAIM'. HALE, LONDON, ENGLAND, ASSIGNOR TO D. GES'IETHER, LIMITED, OF LONDON, ENGLAND.

DUPLICATING.

No Drawing. Application filed September 14, 1925, Serial No. 56,402, and in Great Britain October 2, 1924.

This invention relates to duplicating and has for its object to provide an improved method of preparing stencils adapted more particularly for use in the production of work on a large scale as, for instance, posters and the like, such as hitherto have been ordinarily produced by lithography, by the local application of suitable solvent compositions to a stencil sheet which consists F of a sheet of highly porous material such as yoshino paper furnished with a coating of a composition impermeable to ink.

Hitherto, in the production of such stencils, the ink-resisting coating of the stencil sheets employed has been of a resinous character, the solvent composition being of such character as to enter into chemical reaction with the resinous material to form water soluble or removable bodies.

The present invention consists broadly in applying locally to a stencil sheet comprising a highly porous support such as voshino paper and an ink-resisting coating including a gelatinized organic colloid of the character of gelatine, agar-agar, starch, dextrine, carbohydrate gums or the like, an agent adapted to liquefy or depress the gelating point of the colloid and removing the liquefied colloid.

In the appended claims the expression gelatine is employed as including the gelatinized organic colloids of the character above specified.

The agent employed for liquefying the gelatinized organic colloid will to some extent depend upon the' character of the colloid and bodies included in the so-called Hofmeister series may be employed for instance where the colloid is a protein such as gelatine.

Thus,-for instance, sulphuric acid, a solution of ammonium thiocyanate or sodium iodide may be used.

Conveniently, the 'liquefying agents are employed in association with a colouring medium adapted to render visible the matter produced upon the stencil and also agents adapted to increase their viscosity, the use of bodies for increasing the viscosity of the composition employed as lique ying agent which may in such case be referred to as an ink being designed to prevent the liquefying agents spreading or running to an undue extent.

l '10 this end solids in a suitably finely divided form may be included in the liquefying composition. For instance, carbon black, china clay, bentonite, kieselguhr may be employed, their elfect being to hin-' der lateral penetration or spreading of the liquefying agent probably as the result of capillary attraction or the surface tension relationship between the liquid and solid,

constituents of the composition.

A further feature of the invention comprises the provision of the stencil sheet with, in addition to the porous support, a screen or openwork structure constituted by a material which will not be substantially affected by the liquefying agents used.

This screen or openwork structure may be formed or applied to the stencil sheet in any convenient manner and to the side thereof to which the ink-resting medium has been applied or to the reverse side.

Thus for instance by means of a spraying process a solution of celluloid may be applied to the sheet so as to provide on its surface a plurality of dots of celluloid more or less uniformly distributed over the said surface. n

Alternatively by a printing or other operation a screen composed of lines, dot-s or reticulations of a material adapted to resist the action of the liquefying agents may be formed on the surface of the stencil sheet.

By this means not only is the tendency of the liquefying agent to spread laterally reduced, but a screened effect may be secured in the stencil reproduction which may therefore resemble work done with a chalk and in other cases while the screened effect will not be apparent to the eye the screening will have the effect of limiting the amount of ink passin through the stencil when forming impressions with the aid thereof and thus the consumption of the ink used in duplication will be reduced while the passage of an excessive quantity of ink through the stencil and the production of too heavily inked impressions will be largely prevented and moreover the strength or durability of the stencil will be increased.

For removing the softened colloid a sheet of paper coated with blown rape oil may be used, the sheet being pressed into contact with the face ofthe stencil and then way the adhesive oily material will pick out the softened gelatine from the remainder of the coating of the stencil sheet.

Preferably, however, the softened protein or other colloid is expelled by the ink used in forming stencil impressions .and when the removal of the softened or liquefied protein is effected in this way the stencil sheet, after the matter has been written or otherwise produced thereon, may be mounted upon a duplicating machine adapted for use with an 'oily ink and one or two stencil impressions prepared therefrom in the usual manner, the oily ink forcing its way through the stencil sheet at the points where it has been subjected to the action of the softening agent and effecting the removal of the softened colloid from these portions.

In carrying the invention into effect, sten cil sheets of known character comprising a suitable porous support and an ink-resisting coating including for instance a gelatinized potein and a softening or tempering agent or softening or tempering agents such as glycerine, dextrine, soap or the like may be used.

Where, as the gelatinizing organic colloid, gelatine is used, a proportion of alum or the like may be included in the coating composition.

As above indicated, the invention is applicable to the production of work including heavily inked surfaces or inked areas of considerable size and for this purpose the employment of fine lawn or like textile material as support for the ink-resisting medium ma be suitable.

For pro ucing work of this character also brushes may be used for applying the softening medium for the ink-resistmg coating. When, on the other hand, the invention is applied to the production of finer work a pen or other device adapted to form sufiiciently fine lines will be used while the porous support in such case is preferably yoshino paper.

Preferably in forming the stencil the procedure forming the subject-matter of British application for Letters Patent No. 190 of 1925 is followed.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. lhe method of preparing stencils for use in duplicating which consists in applying locally to a stencil sheet comprising a highly porous support and an ink-resisting coating including gelatine, an agent adapted to liquefy or depress the gelating point of the colloid and removing the liquefied colloid.

2. The method of preparing stencils for use in duplicating which consists in applying locally to a stencil sheet comprising yoshino paper and an ink-resisting coating including gelatine, an agent adapted to liquefy or depress the gelating point of the colloid and removing the liquefied colloid.

3. A stencil sheet for use in the method of preparing stencils comprising a slightly porous support, an ink-resisting coating including gelatine on said support, said coating adapted to be liquefied by the employment of suitable agents used in forming the stencil and a screen or open-work structure which is substantially indicated by the liquefying agents used in forming the stencil.

In testimony whereof I have signed my name to this specification.

DAVID GESTETNER. 

